The digestive system: Challenges and opportunities

The purpose of this review is to set the context for a discussion of the improvement of nutrient efficiency in poultry production through greater understanding of the gastrointestinal (GI) system. Much of the ongoing research in efficiency of nutrient capture is directed toward better understanding of the benefits of nonpharmaceutical antibiotic growth promoters because approvals for the use of nontherapeutic antibiotics in animal feed are fast disappearing worldwide. Acceptable replacements for these drugs are being sought. Because much of the effect of antibiotics is due to their antimicrobial activity, research has been directed at understanding the antimicrobial effect and identifying new nonpharmacological antimicrobials for the industry. However, there are certainly other opportunities for innovative improvements in efficiency through modification of GI development, maintenance, and health. The GI system includes the gut itself, liver, pancreas, gut-associated lymphoid tissue, and resident microflora. All of these tissues and organs offer opportunities for improvement. This review will begin with a description of the components of the GI system, including anatomy, ontogeny, cell biology, and system maintenance. Opportunities to improve efficiency though alterations of GI ontogeny, structure, and function will be discussed briefly. Topics to be covered by other speakers are the role of mitochondria in the partitioning of nutrients from gut maintenance to muscle growth, use of exogenous delivery of antibodies to reduce diversion of nutrients to immunity, and reducing the need for intestinal and hepatic detoxification through the modulation of the animal's own capacity to exclude pathogens and toxins from entering the body.